In playing round with return types I accidentally set all returns from ThingClient as None. The only tests that errored were the ones for blobs. While the coverage is high, there probably needs to be another test suite with some more high level tests. Basically a simple simulation application which handles things like Things calling eachother, calling things over HTTP, something a bit more complex than in a unit test. This will also help with checking that projects using LabThings can be typed.